The overall objective of this proposal is to formulate a more comprehensive understanding of the interactions between the adrenal gland and maintenance of pregnancy in the rat. The deleterious effects of "stress" and high levels of exogenous glucocorticoids on fetal development and maintenance of pregnancy have been reviewed. Two different approaches are taken to study these interactions. The first is to study the kinetics of adrenal 11 beta-hydroxylase to determine if mechanisms have evolved which specifically decrease glucocorticoid production during certain stages of pregnancy. A mechanism of interaction between an "activator" in adrenal cytosol, 11 beta-hydroxylase, and substrate is proposed. Kinetics of the activator is studied with regard to various stages of pregnancy. The influence of the hormones of pregnancy on the kinetics of the activator is also studied. In addition, the physico-chemical nature of the activator is studied by dialysis, sucrose gradient, and gel filtration analysis. The second approach involves a study of the molecular action of progesterone upon placental function. Major aspects include binding to placental cytosol receptors, translocation to the nucleus, acceptor binding, and initiation of RNA synthesis with regard to advancing pregnancy. Experimental observations are then made upon the ability of ACTH and glucocorticoids to disrupt progesterone action. Intervals of pregnancy particularly sensitive to glucocorticoids are noted and evaluated with regard to the kinetic studies of adrenal steroidogenesis.